1. Technical Field
The present disclosure relates to a method for forming a circuit pattern and, more particularly, to a method for forming a circuit pattern by printing, utilizing electrophotography.
2. Background Art
A ceramic multilayer board may include a resistance pattern serving as a resistance element and a circuit pattern including wiring serving as an inductor and/or a capacitor electrode.
For example, a resistance pattern inside a ceramic multilayer board is formed by applying resistive paste to a ceramic green sheet, forming a green laminate composed of the ceramic green sheet and another ceramic green sheet, and firing the green laminate.
A resistance pattern on the surface of a ceramic multilayer board is generally formed by baking resistive paste applied to a fired ceramic multilayer board. A resistance pattern on the surface of a ceramic multilayer board may also be formed by firing resistive paste applied to a green laminate.
The resistance of a resistance pattern may be controlled by the following two methods, alone or in combination.
A first method relies on dimensional control of a resistance pattern. For example, to increase the resistance, the electrode gap is increased, the electrode width is reduced, or the thickness of a printed film is reduced. The reverse of these processes may be performed to reduce the resistance.
A fired thick-film resistor is usually trimmed with a laser to control the resistance with high precision (see, for example, Patent Document 1).
According to a second method, the resistance of a resistance pattern is controlled by the resistance of resistive paste.
With a reduction in the size and the profile of components, the resistance pattern area is also being reduced. It is therefore extremely difficult to alter the resistance of a resistance pattern by altering the dimensions of the resistance pattern. Under these circumstances, the method may be used in which a plurality of resistive pastes having different resistances may be appropriately combined to achieve a desired resistance.
However, this method requires many types of resistive paste having different resistances, thus requiring complicated inventory management and considerable management costs.
Thus, to avoid the complicated management of resistive pastes, a limited number of pastes having different resistances may be blended to provide a desired resistance. Such a blend method, involving a stock of only a limited number of resistive pastes having different resistances (for example, 10, 100, 1000, and 10000 ohms per square), has been widely used (see, for example, Patent Document 2).
Patent Document 1: Japanese Unexamined Patent Application Publication No. 63-261796
Patent Document 2: Japanese Unexamined Patent Application Publication No. 62-290102
However, additional problems still remain to be solved.
A ceramic multilayer board includes many ceramic layers to integrate various circuits. Resistance patterns having different resistances are often integrated on the same layer. To form resistance patterns having different resistances, resistive paste and a printing plate must be replaced by another resistive paste and another printing plate for each of the resistance patterns.
For example, to prepare five resistance patterns having different resistances on a single layer, even the blend method described above needs up to five blends of resistive pastes and five printing plates, thus requiring five cycles of printing while replacing the printing plate and the resistive paste for every resistance pattern.